A= 1+2+22+...+2100
=> 2A= 2+22+24+...+2101
=> 2A-A= ( 2+22+24+...+2101) -( 1+2+22+...+2100)
=> A=2101-1
A = 1 + 2 + 22 + 23 + .... + 2100
2A = 2 + 22 + 23 + 24 + ... + 2101
2A - A = 2 + 22 + 23 + 24 + ... + 2101 - ( 1 + 2 + 22 + 23 + .... + 2100)
A = 2 + 22 + 23 + 24 + ... + 2101 - 1 - 2 - 22 - 23 - .... - 2100
A = 2101 - 1
250 x ( A - 1 ) = 250 x (2101 - 1 - 1) = 250 x 2101 = 2151